Bach did not write a collection titled '42 Little Keyboard Preludes'. This entry likely conflates various small preludes or is a mislabeled collection.
Pay close attention to voice leading and maintaining independent melodic lines.
42 Little Keyboard Preludes is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of 42 Little Keyboard Preludes lasts about 15 minutes.
42 Little Keyboard Preludes is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.